Chiral and trace anomalies in Deeply Virtual Compton Scattering

Abstract

Inspired by recent work by Tarasov and Venugopalan, we calculate the one-loop quark box diagrams relevant to polarized and unpolarized Deep Inelastic Scattering (DIS) by introducing off-forward momentum $l^{\mu }$ as an infrared regulator. In the polarized case, we rederive the pole $1/l^2$ related to the axial (chiral) anomaly. In addition, we obtain the usual logarithmic term and the DIS coefficient function. We interpret the result in terms of the generalized parton distributions (GPDs) $\tilde{H}$ and $\tilde{E}$ and discuss the possible violation of QCD factorization for the Compton scattering amplitude. Remarkably, we also find poles in the unpolarized case which are remnants of the trace anomaly. We argue that these poles are cancelled by the would-be massless glueball poles in the GPDs $H$ and $E$ as well as in their moments, the nucleon gravitational form factors $A,B$ and $D$. This mechanism sheds light on the connection between the gravitational form factors and the gluon condensate operator $F^{\mu \nu }{F}_{\mu \nu }$.

14 pages, 1 figure, minor additions to text, updated references, version to appear in PRD

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Cited by in corpus (5)

• Generalized parton distributions at zero skewness
• Small $x$ Physics Beyond Eikonal Approximation: an Effective Hamiltonian Approach
• Chiral and trace anomalies in Deeply Virtual Compton Scattering II: QCD factorization and beyond
• Generalized parton distributions from the pseudo-distribution approach on the lattice
• Global analysis of polarized DIS & SIDIS data with improved small-$x$ helicity evolution